By Randy Lewis LOS ANGELES -- As Brian Wilson remembers it, the head Beach Boy was still a beach toddler the first time he heard George Gershwin's Rhapsody in Blue, a piece of music that would have a profound effect on the rest of his life."I was 2 years old," Wilson, 68, said recently while seated on the couch in the living room of his Beverly Hills home, his voice carrying the enthusiasm of a discovery made last week.